The present invention relates to a semiconductor manufacture technology to be used in semiconductor processes, and, more particularly, to an exposure technology for charged-particle beam lithography which exposes a pattern on a substrate like a wafer, or a master like a mask or reticle using a plurality of charged-particle beams.
With the recent remarkable advancement on the miniaturization of circuit patterns and high scale integration, the electron beam exposure that is used in fabrication of photomasks demands a higher processing speed as well as a higher accuracy. The direct exposure system which directly exposes a pattern on a wafer using an electron beam and which is promising as the next generation lithography technology faces the throughput as the first challenge for mass production of devices.
To improve the throughput, the electron beam exposure is advancing in the direction of increasing the area of electron beams that can be irradiated at a time. As the point beam system that uses point beams suffers a poor throughput too low for mass production, the variable forming system that uses beams having size-changeable rectangular cross sections has been developed. While the system has a throughput higher by one to two digits than the point beam system, it still has a lot of issues on the throughput that should be cleared for exposure of miniaturized patterns with high integration. Developed in this respect is the cell projection system that makes the cross section of a beam into a desired shape using a cell mask with respect to specific patterns which are frequently used. While this system has a large merit on semiconductor circuits which involve many repetitive patterns, such as a memory circuit, it is hard to achieve for semiconductor circuits which involve few repetitive patterns, such as a logic circuit, because of multiple patterns that should be prepared on a cell mask.
One way to solve the problem is a multibeam system which irradiates a plurality of electron beams on a sample, deflects the electron beams to scan on the sample, and individually turns on or off the electron beams according to a pattern to be exposed, thereby exposing the pattern. Because this system can expose an arbitrary pattern without using a mask, the throughput can be improved further.
Such multibeam electron beam exposing systems are disclosed in, for example, Japanese Patent Application Laid-Open No. 2001-267221 and Japanese Patent Application Laid-Open No. 2002-319532. An example of an electron beam exposing apparatus will be described referring to a schematic diagram in FIG. 1.
Reference symbol “101” denotes a crossover image which is formed by an electron gun. With the crossover 101 being a light source, a condenser lens 102 forms an approximately parallel electron beams. The condenser lens in this example is an electromagnetic lens. Reference symbol “103” is an aperture array having apertures arrayed two-dimensionally. Reference symbol “104” is a lens array having electrostatic lenses having the same focal length arrayed two-dimensionally. Reference symbols “105” and “106” are deflector arrays each having a two-dimensional array of electrostatic deflectors which can be driven individually. Reference symbol “107” is a blanker array having a two-dimensional array of electrostatic blankers which can be driven individually.
The approximately parallel electron beams formed by the condenser lens 102 are split into a plurality of electron beams by the aperture array 103. The split electron beams form intermediate images of the crossover 101 at the height of the blanker array 107 by the respective electrostatic lenses of the lens array 104. At this time, the deflector arrays 105 and 106 individually adjust the paths of the electron beams to cause the associated intermediate images of the electron sources to pass at desired positions in the associated blankers in the blanker array 107.
The blankers in the blanker array 107 individually control whether or not to irradiate the associated electron beams on a sample 115. Specifically, the electron beam that is deflected by the associated blanker is blocked by a blanking restriction 109 and is not irradiated on the sample 115. As the electron beam that is not deflected by the blanker array 107 is not blocked by the blanking restriction 109, the beam is irradiated on the sample 115.
As mentioned above, the aperture array 103, the lens array 104, the deflector arrays 105 and 106, and the blanker array 107 form a plurality of intermediate images of the crossover and control whether or not to irradiate each electron beam on the sample 115. The aperture array 103, the lens array 104, the deflector arrays 105 and 106, and the blanker array 107 together are called a multibeam forming device 108.
The intermediate images of the crossover that are formed by the multibeam forming device 108 and are individually controlled whether or not to be irradiated on the sample 115 are projected in reduced size on the sample 115 set on a stage 116 by electromagnetic lenses 110, 111, 112 and 113. The position of the size-reduced projected image is determined by the amount of deflection by a deflector 114.
For such a multibeam system, a method of detecting the occurrence of a failure and the location of a failure in a blanking aperture array which forms a charged-particle beam has been proposed as disclosed in, for example, Japanese Patent Application Laid-Open No. 11-186144.
Further, Japanese Patent Application Laid-Open No. 2000-43317, for example, proposes a method capable of performing an exposure process even with some LDs broken or unable to emit light in a multibeam exposure apparatus using LDs.